This invention relates to conveyor belts for conveyors of the type in which the conveyor belt is supported and driven by two endless cables, one adjacent each side of the belt. Such belt conveyors are commonly known as "cable belt conveyors" and hereinafter are referred to as belt conveyors of the type described.
Conveyor belts for belt conveyors of the type described are required to be relatively stiff transversely in order to support a load on the belt and relatively flexible longitudinally to permit the belt to pass around end rollers.
A common way to achieve the required transverse stiffness of the belt is to incorporate steel flat bar reinforcing straps in the belt. The straps are incorporated into the elastomeric body of the belt and extend transversely of the belt for almost the full width of the belt. The straps are at spaced intervals along the belt, the spacing being selected according to the desired deflection to be achieved when the belt is fully loaded. While this particular construction does provide the required transverse stiffness in the belt, it has not proved altogether satisfactory as the ends of the reinforcing straps have a tendency to protrude through the elastomeric body of the belt. This arises as a result of transverse shrinkage of the elastomeric material of the belt which occurs during exposure to the high temperature of vulcanisation and subsequent ambient temperature after the vulcanisation process is complete. As shrinkage occurs, the small cross-sectional area at the ends of the reinforcing straps exert concentrated compressive end loads on the elastomeric body with a result that the ends of the straps express their way through the elastomeric body and protrude from it. The protruding straps destroy the integrity of the belt surface and facilitate ingress of extraneous substances such as moisture which can have a damaging effect on the life of the belt.
With a view to overcoming the problems described above in relation to use of reinforcing straps, it has been proposed to reinforce the belt with a reinforcing structure comprising two layers of breaker fabric, one between each side of the elastomeric core of the belt and the adjacent cover layer. The breaker fabric has textile warps which provide longitudinal flexibility for the belt and steel cord wefts which provide lateral stiffness. This construction has also proved not to be altogether satisfactory as damage to one of the cover layers of the belt may expose the breaker fabrics to ingress of moisture which can cause the steel cords to corrode and so weaken the belt to the extent that it can collapse under load.
Against the background of the aforementioned difficulties with the construction of existing conveyor belting, the present invention seeks to provide a novel and useful alternative form of conveyor belt construction.